Medullary Carcinoma of the Colon and Rectum
Supplemental Studies
Immunohistology
- By definition, chromogranin and synaptophysin show at most focal or scattered staining
- One report suggests that calretinin distinguishes medullary carcinoma from poorly differentiated carcinoma NOS
- Medullary 73%
- NOS 12%
- Other markers tested do not provide clear distinction:
CK7
13%
CK20
14%
CDX2
15-20%
MUC1
67%
MUC2
60%
Genetic Analysis
- Frequently MSI unstable
- Usually MLH1 negative
- 80-100% of cases
- Usually MLH1 negative
